In the past the setting up of the rolls of a beam mill prior to rolling has mainly been done by skilled trial and error. Knowing a beam of certain dimensions is required the rolls are, in the practice of the art, set to approximately the correct spacing using the roll adjustment gear, and a trial length of beam is run off. The dimensions of the resulting beam are then checked and compared with the requirements, and the positions of the horizontal and vertical rolls of the beam mill adjusted to diminish any error. A further trial length of beam is run off, and the procedure repeated for as many times as it takes to bring the produced beam dimensions within the tolerances of the required product. Clearly this method is both wasteful of raw materials and time.
It has been suggested to apply automatic gap control technology as used on strip mills, to beam mills. Thus accurate positioning becomes possible, but the existing method of setting up by trial and error are not suited to the new technology, and certainly do not take advantage of the accuracy possible with such a feedback system. The known AGC systems have a sensor which detects the pressure applied to a roll by sensing the pressure in a hydraulic capsule supporting the roll chock, and another sensor which detects the actual position of the roll and senses any variation in that position. In strip mills the sensed variations in hydraulic pressure in the capsule is used during rolling to correct the rolling load. The position sensors are used to initialise the positions of the pair of rolls used.
A major deficiency with the prior approach was the lack of any proper relative alignment of the rolls prior to rolling commencing.